Advances in nanoscience and nanotechnology research hinge on the ability to fabricate/manipulate nano-sized structures at desired locations on any given substrate. While several growth methods have been developed, most of these fall short of the desired goals. For example, gold or silver nanoparticles can be readily prepared via chemical routes, but coaxing them to lay in an ordered array warrants the use of time consuming atomic force microscopy (AFM)-based or scanning tunneling microscopy (STM)-based techniques.
The current state of the art in nanopillar and nanoparticle array formation involves methods such as the following: evaporating or electrochemically depositing gold onto templated surfaces such as alumina, followed by the removal of the template; colloidal lithography, where the self-arrangement of spherical colloid particles provides evenly-spaced voids that can be filled by metal; Focused Ion Beam (FIB) milling, where a thin film of metal is deposited on a substrate, and regular structures are patterned out of it by the controlled ion beam, or by forming holes in a photoresist, followed by filling of the holes with metal; and electron beam lithography (EBL), in which utilizing a scanning electron microscope (SEM), patterns are drawn on a photoresist, followed by deposition of metal into the resulting pattern. Though each of the above methods can produce regularly spaced nanopillars or nanoparticles with reasonable control of aspect ratio, each method is, to varying degrees, time consuming, step-involved, and expensive. Conversely, though simple evaporation deposition of metallic nanoparticles from a colloid onto a substrate is fast and inexpensive, the arrays produced do not exhibit regular particle-particle spacing, and the size and shape of individual particles are not uniform. The limitations of these methods have created a bottleneck between the study of the fundamental characteristics of patterned nanostructures and the utilization of such technology in scaled-up, mass-produced devices.
What are needed in the art are simpler, more economical methods and devices for forming patterns on a substrate on micro- and nanosized scales.